Picture proposed for a qualitative explanation of the Segment I variability. The lighter semi-ring represents the 16–20 R_⊙ disc inhomogeneity in three rotational phases. The disc fluxes calculated for V filter are expressed in greyscales (as defined on respective bars) and are left in temporary model units; they are also slightly affected by limitations of our plotting software. The stellar flux is expressed arbitrarily; the stellar radius was set to 1.5 R_⊙.